The present invention relates to an apparatus for slitting web-like materials to a predetermined width.
There are known apparatus for slitting web-like materials such as photographic films, papers, fabrics, belt-shaped thin steel plates and the like (which are generically called web materials in this specification) to a predetermined width, which are provided with pairs of slitting means, each pair comprising upper and lower slitting edges which are mounted on a supporting frame for rotation. The supporting frames are adapted to move toward and away from each other so as to adjust the edge-to-edge distance to a predetermined width to which the web material is to be slit.
Upon being slit, the web material is carried by the lower slitting edges at both margins thereof, but it usually deflects either downward due to its own weight if it is flexible or upward if it is stiff to some degree. This deflection makes the web material be split widen a little more than intended the edge-to-edge distance, even though the equipment is adjusted to a desired width.
For preventing such lateral deflection, and to slit the web material precisely to a desired width, prior Japanese Patent Unexamined Publication No. 57-163012 teaches an apparatus provided with a pair of superposed rolls for holding down the web material, and alternately prior Japanese Utility Model Unexamined Publication No. 58-13920 teaches an apparatus provided with a pair of narrow spacers adjacent the lower slit edges.
The apparatus disclosed in these prior unexamined publications has a problem which makes it as difficult as ever to slit the web material precisely to a desired width, in particular when the web material to be slit is relatively wide. The reason is that, because either the superposed rollers or the spacers are fixed to the supporting frames or to a stationary part of the apparatus, the supported width of web material relative to the overall width thereof will be reduced as the edge-to-edge distance is increased in order to slit relatively wide web materials, and the wide web materials will deflect due to their own weight or stiffness.